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Guide · updated 2026-08-16

How to Install a Rare Breed FRT-15

A clear, safety-first walkthrough for installing an FRT in a standard AR-15 lower — and the parts you need around it.

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The RBT Editorial Desk · Firearms parts research & buyer education
AR-15 & HK-platform trigger research · fitment and compliance focus

Safety first: clear the firearm. Remove the magazine, lock the bolt to the rear, and visually and physically confirm the chamber is empty before you begin. Work on an unloaded firearm only.

What you need first

The FRT drops into a standard AR-15 lower, but the bolt carrier and buffer are what make it reset reliably — see our buffer & BCG guide.

Install steps (overview)

  1. Separate the upper and lower receivers.
  2. Remove your existing fire-control group (trigger, hammer, and their pins).
  3. Install the FRT unit per Rare Breed's included instructions, seating the trigger and hammer and driving the pins.
  4. Install the full-auto/M16 bolt carrier in the upper and the H2/H3 buffer in the buffer tube.
  5. Reassemble, then function-check with the firearm unloaded: confirm safe operation, correct reset, and that the safety works before live fire.

Follow the manufacturer's printed instructions as the authority for your specific unit. If you are not fully comfortable working on an AR-15 fire-control group, have a qualified gunsmith install and function-check it. Improper installation can cause malfunctions or unsafe conditions.

This page is general information, not legal advice. Firearm law changes and varies by jurisdiction. Confirm the current law where you live before ordering, and consult a qualified attorney if you are unsure.

Shop these models:
FRT-15L3

Frequently asked questions

Is the FRT-15 drop-in?
It installs in a standard AR-15 lower, but for reliable reset you generally need a full-auto/M16 bolt carrier and an H2 or H3 buffer.
Do I need a gunsmith to install an FRT?
Many builders do it themselves following the included instructions, but professional installation and a function check are recommended if you're unsure.
Why won't my FRT reset?
The most common causes are a non-full-auto bolt carrier or too light a buffer. See our buffer and BCG guide.